Ceiling fans have been around for many years as a useful air circulator. The popular blade style over the years is a flat planar rectangular blade that can have a slight tilt, as shown for example in U.S. Pat. Nos. Des. 355,027 to Yound and Des. 382,636 to Yang. These patents while moving air are not concerned with maximizing optimum downward airflow. Furthermore, many of the flat ceiling fan blades have problems such as poor performance at high speeds, wobbling, and excessive noise that is noticeable to persons in the vicinity of the fan blades.
Aircraft, marine and automobile engine propeller type blades have been altered over the years to shapes other than flat rectangular. See for example, U.S. Pat. Nos. 1,903,823 to Lougheed; 1,942,688 to Davis; 2,283,956 to Smith; 2,345,047 to Houghton; 2,450,440 to Mills; 4,197,057 to Hayashi; 4,325,675 to Gallot et al.; 4,411,598 to Okada; 4,416,434 to Thibert; 4,730,985 to Rothman et al. 4,794,633 to Hickey; 4,844,698 to Gornstein; 5,114,313 to Vorus; and 5,253,979 to Fradenburgh et al.; Australian Patent 19,987 to Eather. However, these patents are describing devices that are generally used for high speed water, aircraft, and automobile applications where the propellers are run at high revolutions per minute(rpm) generally in excess of 500 rpm. None of these propellers are designed for optimum airflow at low speeds of less than approximately 200 rpm which is the desired speeds used in overhead ceiling fan systems.
Some alternative blade shapes have been proposed for other types of fans. See for example, U.S. Pat. Nos. 1,506,937 to Miller; 2,682,925 to Wosik; 4,892,460 to Volk; 5,244,349 to Wang; Great Britain Patent 676,406 to Spencer; and PCT Application No. WO 92/07192.
Miller '937 requires that their blades have root “lips 26” FIG. 1 that overlap one another, and would not be practical nor useable for three or more fan blade operation for a ceiling fan. Wosik '925 describes “fan blades . . . particularly adapted to fan blades on top of cooling towers such for example as are used in oil refineries and in other industries . . . ”, column 1, lines 1–5, and does not describe any use for ceiling fan applications. The Volk '460 patent by claiming to be “aerodynamically designed” requires one curved piece to be attached at one end to a conventional planar rectangular blade. Using two pieces for each blade adds extreme costs in both the manufacturing and assembly of the ceiling itself. Furthermore, the grooved connection point in the Volk devices would appear to be susceptible to separating and causing a hazard to anyone or any property beneath the ceiling fan itself. Such an added device also has necessarily less than optimal aerodynamic properties.
Wang '349 requires each of their blades be “drilled with a plurality of perforations . . . for reducing weight . . . (and) may be reinforced by at least one rib . . . ”, abstract. Clearly, such a blades would not be aesthetically pleasing to the user to have various holes and ribs visible on the blades, and there is no description for increasing airflow with such an arrangement. Great Britain Patent '406 describes “. . . fan impellers” that require an “. . . unitary structure . . . constituted by a boss and four blades . . . ” page 1, lines 38+, and does not describe any single blades that can be used without any central boss type hub arrangement nor any use for less than three or more than four blade operation that will allow versatility for mounting separate numbers of blades on a ceiling fan motor. PCT '192 is for use “in an electric fan . . . to convert axially existing ambient air into a radially outward current of air . . . ”, abstract, and is shown in FIGS. 5–12 as being used for being mounted on “post(s)”, and the like, and is not directed toward a ceiling fan operation, which would direct air primarily downward. Additionally, PCT '192 generally requires an elaborate arrangement of using plural blades angled both upward and downward for operation.
U.S. Pat. No. 6,244,821 to Boyd et al. describes a ceiling fan of covering large blades of between 15 feet(180 inches) to approximately 40 feet(480 inches) which can not be used for conventional applications such as those used in homes and offices.
U.S. Pat. Nos. 34,109 and 4,844,698 to Gornstein describes sixty inch blades for use vehicles such as hovercrafts, airboats, and dirigibles which have no application to being used as ceiling fans.
U.S. Pat. No. 5,860,788 to Sorensen mentions some old uses of having four to six blade fans that cover approximately 5 feet(60 inches) but has not no data on low speed operation, nor on using three blades, nor on using any twisted blade configurations, and would not have enhanced efficiency over conventional ceiling fan operation.
Although larger ceiling fans with diameters greater than 54 inches have been produced, these fans have not incorporated enhancements to the fan blade, such as maximizing twist, taper and air foil configurations to optimize air moving performance.
Thus, the need exists for better performing ceiling fans over the prior art.